1. Field of the Invention
The present invention relates to an apparatus for applying a primer as an adhesion assistant to a surface of a workpiece such as an automobile window glass panel, and an apparatus for wiping such a surface before a primer is applied thereto.
2. Description of the Prior Art
Automobile window glass panels are assembled on automobile bodies usually as follows: A primer as an adhesion assistant is applied to the peripheral edge of an automobile window glass panel, and then an adhesive is coated on the peripheral edge of the glass panel over the primer coating. Thereafter, the glass panel is bonded to an automobile body by the adhesive.
Efforts have been made to automate the process of applying a primer to an automobile window glass panel. An example of automatic primer applying apparatus is disclosed in Japanese patent publication No. 62-23613 (corresponding to U.S. Pat. No. 4,605,569).
The disclosed primer applying apparatus has a coating brush for applying a primer to an automobile window glass panel. The coating brush is resiliently supported on the distal end of a robot arm through an air cylinder and a spring. To coat a primer, the coating brush is pressed against the peripheral edge of the glass panel, which is held in a working station, by the robot. Then, while the primer is being supplied to the coating brush, the robot arm is moved along a path that the robot has been trained to follow for thereby moving the coating brush along the peripheral edge of the glass panel to apply a primer coating to the peripheral edge.
Since, however, the coating brush tends to be deformed or some of the primer supplied to the coating brush cakes before being coated to the glass panel, it has been difficult to keep the coating brush in contact with a uniform area of the glass panel, and also to supply a uniform amount of primer to every portion of the coating brush which is to contact the glass panel. For these reasons, the glass panel is liable to have primer coating irregularities. Therefore, it has been necessary to inspect the coated glass surface for such primer coating irregularities or similar defects. If any primer coating irregularities or defects are found, they should be removed as by applying the primer again. These inspecting and mending processes are complex as they require a number of steps and a large expenditure of time and labor.
The coating brush should be frequently serviced or replaced with a new one because of brush deformation or primer caking or solidification. The brush replacement is however laborious and costly.
According to the disclosed primer applying apparatus, when the coating brush is not in use, it is placed in a sealed container and an inert gas is supplied into the container for preventing the primer attached to the coating brush from caking. The disclosed arrangement is however not fully effective to prevent the primer attached to the coating brush from caking because the primer gradually cakes even while the coating brush is moving to the container.
Before a primer is applied to an automobile window glass panel, it is customary practice to wipe the surface of the glass panel to which the primer is to be coated, thus removing dust, fingerprints, or oily films off the glass panel surface.
Japanese patent publication No. 1-17912 shows an automatic apparatus for wiping the surface of an automobile window glass panel to which a primer is to be coated.
The disclosed automatic wiping apparatus has an elongated piece of wiping cloth gripped by a gripper on the distal end of a robot arm and resiliently supported by an air cylinder and a spring. To wipe the glass panel surface, the piece of wiping cloth gripped by the gripper is pressed against the peripheral edge of the glass panel, which is held in a working station, by the robot. Then, while a wiping solution is being supplied to the piece of wiping cloth, the robot arm is moved along a path that the robot has been trained to follow for thereby moving the piece of wiping cloth along the peripheral edge of the glass panel to wipe the peripheral edge.
After the glass panel is wiped by the piece of wiping cloth, it is replaced with a new piece of wiping cloth. More specifically, the used piece of wiping cloth is released from the gripper, and then a new piece of wiping cloth is gripped by the gripper. The new piece of cloth is supplied from a wiping cloth supply. The wiping cloth supply has a coiled web of wiping cloth and a cutter for cutting the web of wiping cloth into an elongated piece of wiping cloth which is to be gripped by the gripper. After having released the used piece of wiping cloth, the gripper grips one end of the coiled web of wiping cloth and pulls it from the wiping cloth supply. The pulled web of wiping cloth is then cut off into a new piece of wiping cloth by the cutter. The gripper now grips the new piece of wiping cloth for use on another automobile window glass panel.
Inasmuch as the gripper grips a piece of wiping cloth, the piece of wiping cloth must have a portion to be gripped by the gripper, in addition to its portion that is used to wipe a glass panel surface. Therefore, the piece of wiping cloth has to be longer than its portion that is actually used for wiping a glass panel surface. The length of wiping cloth that is consumed is large and uneconomical, resulting in an increase in the cost.
The process of wiping cloth replacement is inefficient because it is composed of many steps, i.e., releasing the used piece of wiping cloth from the gripper, gripping and pulling the web of wiping cloth by the gripper, and cutting the web of wiping cloth into a new piece of wiping cloth by the cutter.